Base62 encode, decode https://github.com/odan/base62js 0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ

Base62.js

if (!$d) {
    var $d = {}
}
$d.BitStream = function BitStream(options) {
    this.Source = [];
    if (typeof options === 'object') {
        this.Source = options
    }
    if (typeof options === 'number') {
        var dim = Math.floor(options);
        this.Source = new Array(dim)
    }
    this.Position = 0;
    this.Length = function() {
        return this.Source.length * 8
    };
    this.Read = function(buffer, offset, count) {
        var tempPos = this.Position;
        tempPos += offset;
        var readPosCount = 0;
        var readPosMod = 0;
        var posCount = tempPos >> 3;
        var posMod = (tempPos - ((tempPos >> 3) << 3));
        while (tempPos < this.Position + offset + count && tempPos < this.Length()) {
            if (((this.Source[posCount]) & (0x1 << (7 - posMod))) != 0) {
                buffer[readPosCount] = ((buffer[readPosCount]) | (0x1 << (7 - readPosMod)))
            } else {
                buffer[readPosCount] = ((buffer[readPosCount]) & (0xffffffff - (0x1 << (7 - readPosMod))))
            }
            tempPos++;
            if (posMod == 7) {
                posMod = 0;
                posCount++
            } else {
                posMod++
            } if (readPosMod == 7) {
                readPosMod = 0;
                readPosCount++
            } else {
                readPosMod++
            }
        }
        var bits = (tempPos - this.Position - offset);
        this.Position = tempPos;
        return bits
    };
    this.Seek = function(offset, origin) {
        switch (origin) {
            case (1):
                {
                    this.Position = offset;
                    break
                }
            case (2):
                {
                    this.Position += offset;
                    break
                }
            case (3):
                {
                    this.Position = this.Length() + offset;
                    break
                }
        }
        return this.Position
    };
    this.Write = function(buffer, offset, count) {
        var tempPos = this.Position;
        var readPosCount = offset >> 3,
            readPosMod = offset - ((offset >> 3) << 3);
        var posCount = tempPos >> 3;
        var posMod = (tempPos - ((tempPos >> 3) << 3));
        while (tempPos < this.Position + count && tempPos < this.Length()) {
            if (((buffer[readPosCount]) & (0x1 << (7 - readPosMod))) != 0) {
                this.Source[posCount] = ((this.Source[posCount]) | (0x1 << (7 - posMod)))
            } else {
                this.Source[posCount] = ((this.Source[posCount]) & (0xffffffff - (0x1 << (7 - posMod))))
            }
            tempPos++;
            if (posMod == 7) {
                posMod = 0;
                posCount++
            } else {
                posMod++
            } if (readPosMod == 7) {
                readPosMod = 0;
                readPosCount++
            } else {
                readPosMod++
            }
        }
        this.Position = tempPos
    }
};
$d.Base62CodingSpace = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
$d.encodeBase62ToString = function encodeBase62ToString(original) {
    var sb = [];
    var stream = new $d.BitStream(original);
    var read = [];
    read.push(0);
    while (true) {
        read[0] = 0;
        var length = stream.Read(read, 0, 6);
        if (length == 6) {
            if ((read[0] >> 3) == 0x1f) {
                sb.push($d.Base62CodingSpace.charAt(61));
                stream.Seek(-1, 2)
            } else if ((read[0] >> 3) == 0x1e) {
                sb.push($d.Base62CodingSpace.charAt(60));
                stream.Seek(-1, 2)
            } else {
                sb.push($d.Base62CodingSpace.charAt((read[0] >> 2)))
            }
        } else {
            sb.push($d.Base62CodingSpace.charAt((read[0] >> (8 - length))));
            break
        }
    }
    var str = sb.join('');
    return str
};
$d.decodeBase62ToArray = function decodeBase62ToArray(base62) {
    var count = 0;
    var stream = new $d.BitStream(base62.length * 6 / 8);
    var len = base62.length;
    for (var i = 0; i < len; i++) {
        var c = base62.charAt(i);
        var index = $d.Base62CodingSpace.indexOf(c);
        if (count == base62.length - 1) {
            var mod = (stream.Position % 8);
            stream.Write([(index << (mod))], 0, 8 - mod)
        } else {
            if (index == 60) {
                stream.Write([0xf0], 0, 5)
            } else if (index == 61) {
                stream.Write([0xf8], 0, 5)
            } else {
                stream.Write([index], 2, 6)
            }
        }
        count++
    }
    var result = new Array(stream.Position / 8);
    stream.Seek(0, 1);
    stream.Read(result, 0, result.length * 8);
    return result
};
$d.encodeBase62 = function encodeBase62(str) {
    if (typeof str !== 'string' || str === '') {
        return ''
    }
    str = str.toString();
    var bytes = [];
    var len = str.length;
    for (var i = 0; i < len; i++) {
        bytes.push(str.charCodeAt(i))
    }
    var strReturn = this.encodeBase62ToString(bytes);
    return strReturn
};
$d.decodeBase62 = function decodeBase62(str) {
    if (typeof str !== 'string' || str === '') {
        return ''
    }
    str = str.toString();
    var bytes = this.decodeBase62ToArray(str);
    var sb = [];
    var len = bytes.length;
    for (var i = 0; i < len; i++) {
        sb.push(String.fromCharCode(bytes[i]))
    }
    str = sb.join('');
    return str
};
(function($) {
    $.encodeBase62 = function encodeBase62(str) {
        return $d.encodeBase62(str)
    };
    $.decodeBase62 = function decodeBase62(str) {
        return $d.decodeBase62(str)
    }
});